'The bacteria found are opportunistic pathogens -– the source of human disease. These should not be present at any level – never mind the significant numbers found.'

At Costa Coffee, seven out of ten samples of ice tested were found to be contaminated with bacteria found in faecal matter.

Meanwhile at both Starbucks and Caffe Nero, three out of 10 samples contained faecal bacteria.

All three chains are currently taking action, with Costa saying: 'We were disappointed with the findings, especially as these stores are all rated "very good" with a the top hygiene rating of five.

'Following these results we took immediate action to review our food safety procedures and have updated our ice-handling guidelines and are in the process of introducing new ice equipment storage across our estate.'

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A spokesperson for Starbucks said they take hygiene 'extremely seriously' and 'nothing is more important' than customer safety.

A Caffe Nero spokesperson said that the findings were 'concerning', adding: 'A thorough investigation is now under way and the appropriate action will be taken.

'Ninety-nine per cent of our stores are rated as very good, good or satisfactory by their local EHO (environmental health officer) – making us one of the most highly rated businesses on the high street,' they added.